Thomas Aquinas

“ Wherefore the mind's application to knowledge precedes its application to those things to which man is directed by his knowledge. Hence study regards knowledge in the first place, and as a result it regards any other things the working of which requires to be directed by knowledge. Now the virtues lay claim to that matter about which they are first and foremost; thus fortitude is concerned about dangers of death, and temperance about pleasures of touch. Therefore studiousness is properly ascribed to knowledge. ”

“ But as regards knowledge, man has contrary inclinations. For on the part of the soul, he is inclined to desire knowledge of things; and so it behooves him to exercise a praiseworthy restraint on this desire, lest he seek knowledge immoderately: whereas on the part of his bodily nature, man is inclined to avoid the trouble of seeking knowledge. Accordingly, as regards the first inclination studiousness is a kind of restraint, and it is in this sense that it is reckoned a part of temperance. ”

“ Now just as in respect of his corporeal nature man naturally desires the pleasures of food and sex, so, in respect of his soul, he naturally desires to know something; thus the Philosopher observes at the beginning of his Metaphysics i, 1: "All men have a natural desire for knowledge."
The moderation of this desire pertains to the virtue of studiousness; wherefore it follows that studiousness is a potential part of temperance, as a subordinate virtue annexed to a principal virtue. ”